# Search results

1. ### Conceptual Problems with Random Variables and Sample Theory

Hi I'm having a few conceptual difficulties with random variables and I was hoping someone could clear up a few things for me: 1) Firstly, what exactly do we mean when we say that two random variables X and Y are equal. I understand what identically distributed means, but my difficulty is with...
2. ### Information Faster Than Light - Thought Experiment

A push is a compression wave. Travels at the speed of sound in that medium. At any rate, the forces between the atoms are fundamentally electromagnetic in nature, so a 'push' cannot be transmitted at a speed greater than that of light. yes. they would.
3. ### The rigid rotator and Angular momentum.

yeah. that makes sense. I was confusing myself. Thanks.
4. ### The rigid rotator and Angular momentum.

If spherical harmonics are simultaneous eigenfunctions of \hat{L} and \hat{L}_{z}, then that means for a state at which l=1, and where you have three possible values of m (1, 0 , -1) that the value of L and L_{z} cannot really be determined simultaneously. Because the three fold degeneracy of...
5. ### Newton's 3rd Law is confusing me

I'm sorry. You're right. There is a net force on the container from the fluid. You'd think you have this stuff down to a tee after 2 years of advanced high school physics. *sigh* ... keep slipping up.
6. ### Newton's 3rd Law is confusing me

If your reference frame is inertial, then the fluid accelerates with the train (Once it's free surface has achieved the stated configuration of course. We cannot analyze the hydrodynamical situation here ... That would be messy. I'm simply talking about the final hydrostatic configuration ) This...
7. ### Physics behind flow of water from a bottle

Where is this vacuum present? If it's present throughout your system, then the water flow won't terminate until all the water from the bottle has flown into the bigger container (Because there's no air pressure to counter the weight of the water in the bottle ) If you're talking about vacuum...
8. ### The state of a hydrogen electon ?

Wow. Thanks a ton. That cleared up the whole mess of ideas in my head for me.
9. ### The state of a hydrogen electon ?

The eigenstates of a hydrogen atom are stationary states with definite values of energy. Now, as I understand it, the quantum mechanical state of the electron in the hydrogen atom is really a linear superposition of all these energy eigenstates. So this should mean that there is a finite...
10. ### Special Relativity and Biological Clocks.

Thanks. That derivation seems to intensely mathematical for me, but i shall try to figure it out. So the whole thing can be traced back to the fact that physical laws should be invariant under certain kinds of transformations ?
11. ### Special Relativity and Biological Clocks.

The bouncing of a ball is a periodic event. So counting the number of bounces is the same as using a watch is it not? A watch essentially counts a recurring periodic event. So if you say that the number of bounces is invariant, then I have in fact devised a clock which is invariant at near light...
12. ### Special Relativity and Biological Clocks.

Does this derivation use light clocks? I would just like to see an argument that isn't hinged on the use of light clocks. Could you send me a link where they derive it formally without the use of light clocks ?
13. ### Special Relativity and Biological Clocks.

Thanks. That clears up a lot of things for me. I'm just confused about why use light to derive lorentz transformations. Does it have to do with the fact that we 'see' everything? Isn't information available to us via sound as well? Why not use sound to derive everything ? In that case would you...
14. ### Special Relativity and Biological Clocks.

Thanks. But this assumes that time dilation is true. My concern is with showing that it is true. So, why exactly would the vector quantities not add vectorially as in the galilean sense ? Can we show that they shouldn't add vectorially near light speeds without invoking light clocks ? Can we use...
15. ### Special Relativity and Biological Clocks.

So you're saying you could derive the time dilation equation by using the bouncy ball method too ? Has this been done anywhere ?
16. ### Special Relativity and Biological Clocks.

By 'recording a time interval' I mean counting the number of ball bounces.
17. ### Special Relativity and Biological Clocks.

the shuttle carrying the ball moves at a speed v relative to the earth observers frame, so after every bounce, the observer on earth sees the ball moving at a horizontal speed v in addition to the vertical speed it has. So Though the ball follows a longer path as seen from the observer on earth...
18. ### Special Relativity and Biological Clocks.

I'm sorry, I don't understand at all what you mean by 'aging of light' .
19. ### Special Relativity and Biological Clocks.

I'm sorry. I'm still very confused. What if the twin in the space shuttle bounces a ball to keep time (say there's no air friction ). Since this is a periodic phenomenon, it's a valid way to keep time. But an observer on earth will record the same time interval for any two events that the...
20. ### Special Relativity and Biological Clocks.

But it doesn't hold for sound clocks does it ? If the speed of sound is different in different inertial frames of reference, then sound clocks wouldn't display time dilation ? I say this because the argument in my textbook that derives the time-dilation relation seems to hinge on using a light...
21. ### Special Relativity and Biological Clocks.

Why does light have to be this 'ultimate' signal then ? What if we use sound for all our timekeeping ? Do the postulates of relativity not hold if the signal is mechanical rather than electromagnetic ? And i'll make my other question more specific then. Would a person who travels for 20 years...
22. ### Special Relativity and Biological Clocks.

Hi. So the whole premise of special relativity seems to me to be hinged on the immutability of the speed of light, the fact that it is the same for every inertial frame of reference, and the fact that information and energy cannot travel faster than this. What really puzzles me is this whole...
23. ### > Why Change Of Magnetic Flux Induces Current In It?

oh. I'm sorry. My bad then.
24. ### Question about AC circuits

To answer your second question, it is counterproductive if you don't want your energy stored in magnetic fields. Inductors are a crucial part of oscillator circuits for example.
25. ### Question about AC circuits

Electric information is transmitted as a guided electromagnetic wave at the speed of light. So every electron along the wire 'learns' that a source of emf has been applied across the circuit almost instantaneously. But you know that the electron drifts at a very tiny speed ( compared to it's...
26. ### > Why Change Of Magnetic Flux Induces Current In It?

As far as classical electrodynamics goes ( I don't know if more advanced theories of physics shed more light on this question ) this is one of maxwell's four fundamental postulates ( or equations ) of electrodynamics. So within the framework of the classical theory, this is simply how it works...
27. ### Quasi-Mathematical Books on Various Topics in Modern Physics.

Just what I was looking for. Thanks a ton Demystifier. :)
28. ### Quasi-Mathematical Books on Various Topics in Modern Physics.

Thanks. Know of anything similar in other topics of modern physics ?
29. ### Quasi-Mathematical Books on Various Topics in Modern Physics.

Can someone provide me with a quasi-mathematical introductory text to quantum field theory ? Ideally, a book that's somewhere between popular science and an introductory freshman physics text. I have a strong background in calculus, having just completed a one-semester equivalent reading of...
30. ### A bar spinning with unlimited angular velocity

I don't know of any physics by which a neutral spinning bar generates a magnetic field. I hope this isn't a relativistic effect. And could you kindly outline the mechanism by which the bar would heat up even in the vacuum of space.